On this occasion Harold's friends gave him, with due formalities, the degree of E. E., which they said meant electrical expert, and ever since that night he has been called "the expert." I inquired of the young folks, as their party was breaking up, if they understood Harold's explanations of all these things, and he replied that he at any rate understood them better having attempted to explain them.
XXIII
TELEGRAPHING BY ELECTRIC WAVES
Fig. 194
The next time Harold and I experimented we arranged something to save us the trouble of tapping the coherer each time we used it. We employed simply an electric bell, B ([Fig. 194]), from which we removed the gong. By reference to the figure the arrangement will be understood. Each time ether waves cause the metal filings to cohere and the battery B1 closes the relay R, battery B2 causes the hammer of B3 to tap against the coherer. This causes the current to cease to flow from B1 and the relay opens again by its own spring.
